Vibration-type measuring sensor

ABSTRACT

This sensor ( 1 ), for a fluid and suitable for use in a pipeline at least temporarily containing the fluid flowing therethrough, has at least one curved measuring tube ( 4, 5 ), which vibrates during operation and guides the fluid, and a housing enclosing the measuring tube. The housing is composed of a metal cap ( 7 ) of two cap halves ( 71, 72 ) and a supporting tube ( 6 ), in which the measuring tube is held at its inlet and outlet ends in a manner such that the tube can oscillate, and out of which a measuring tube segment protrudes sideways. Each cap half has an edge ( 73; 74 ) with, in each case, four edge portions ( 731, 732, 733, 734; 741, 742, 743, 744 ). The edge portions ( 731; 741 ) are straight, the edge portions ( 732, 733; 742, 743 ) are curved, and the edge portions ( 734; 744 ) have the shape of circular arcs. The edge portions ( 731, 732, 733; 741, 742, 743 ) are welded continuously to the supporting tube ( 6 ) and the edge portions ( 734; 744 ) are welded continuously to one another. The cap halves ( 71, 72 ) are cut out of a dish-shaped intermediate ( 70 ) having a formed, surrounding edge bead ( 701 ), provided with the shape of a quarter-torus by metal spinning.

FIELD OF THE INVENTION

The invention relates to a vibration-type measuring pickup or sensor fora fluid to be measured. The sensor is suitable for installation in apipeline at least temporarily containing fluid flowing therethrough.

BACKGROUND OF THE INVENTION

Such sensors usually include at least one curved measuring tube forguiding the fluid and at least one housing surrounding the measuringtube. The measuring tube vibrates during operation.

The main representatives of such sensors are mass-flow/density/viscositysensors operating on the Coriolis principle. These sensors can not onlybe used to measure the instantaneous mass flow of the fluid flowing inthe pipeline, but also the density of the fluid, on the basis of theinstantaneous oscillation frequency of the measuring tubes, and theviscosity of the fluid, on the basis of the power required to maintaintheir oscillations, as well as the temperature of the fluid. The massflow is, by definition, the mass of fluid flowing through each measuringtube cross section per unit time.

U.S. Pat. No. 4,876,898 describes a Coriolis mass flow sensor for use attemperatures up to 220° C. This sensor, which is suitable for use in apipeline at least temporarily containing fluid flowing therethrough,includes:

two parallel, curved measuring tubes that vibrate during operation andguide the fluid,

a metal housing covering the measuring tubes, and

a supporting arrangement of metal,

in which the measuring tubes are held at their inlet and outlet ends ina manner such that the tubes can oscillate, and

out of which the measuring tubes protrude sideways,

which metal housing includes a first cap half and a second cap half forenclosing the measuring tubes,

an edge of which first cap half includes a circular-arc-shaped firstedge portion lying in a first plane and having a first radius ofcurvature and a circular-arc-shaped second edge portion lying in asecond plane perpendicular to the first plane and having a second,significantly smaller, radius of curvature, and

an edge of which second cap half includes a circular-arc-shaped thirdedge portion lying in a third plane and having the first radius ofcurvature and a circular-arc-shaped fourth edge portion lying in afourth plane perpendicular to the third plane and having the secondradius of curvature,

wherein the first and second edge portions are welded continuously toone another, and

wherein the second and the fourth edge portions are welded continuouslyto the supporting arrangement.

Additionally, U.S. Pat. No. 5,301,557 describes a Coriolis mass flowsensor, which is suitable for use in a pipeline at least temporarilycontaining fluid flowing therethrough and which includes:

two parallel, curved measuring tubes that vibrate during operation andguide the fluid,

a supporting arrangement of metal,

in which the measuring tubes are held at their inlet and outlet ends ina manner such that the tubes can oscillate, and

out of which the measuring tubes protrude sideways, and

a curved metal tube completely enclosing the measuring tubes,

which follows the route of the measuring tubes, while maintaining auniform spacing therefrom, and

which, after having been bent to match the route of the measuring tubesand then temporarily divided into two equal tube halves along alongitudinal cutting plane, is then assembled to enclose the measuringtubes and put back together again by welding of the tube halves to oneanother, and

whose ends are welded continuously with the supporting arrangement.

The mentioned U.S. Pat. No. 5,301,557 also describes a Coriolis massflow sensor, which is suitable for use in a pipeline at leasttemporarily containing fluid flowing therethrough and which includes:

two parallel, curved measuring tubes that vibrate during operation andguide the fluid,

a supporting arrangement of metal,

in which the measuring tubes are held at their inlet and outlet ends ina manner such that the tubes can oscillate, and

out of which the measuring tubes protrude sideways, and

a metal tube completely enclosing the measuring tubes and composed ofsectionally straight tube portions terminally welded to one another,

which are made from deep-drawn half-shells continuously welded to oneanother following their placement around the measuring tubes.

Finally, a Coriolis mass-flow/density sensor is offered by theEndress+Hauser group of firms under the label Promass F. This sensor,which is suitable for use in a pipeline at least temporarily containingfluid flowing therethrough, includes:

two parallel, curved measuring tubes that vibrate during operation andguide the fluid,

a metal housing enclosing the measuring tubes,

having a supporting tube of metal,

in which the measuring tubes are held on their inlet and outlet ends ina manner such that the tubes can oscillate, and

out of which measuring tube segments protrude sideways through twocutouts, and

having a deep-drawn metal cap for covering the measuring tube segments,

an edge of which is continuously welded with the supporting tube.

The deep drawing of shaped bodies of metal, including also theabove-mentioned metal caps, is done in a corresponding metaldeep-drawing die, the manufacturing costs of which are very high. Deepdrawing is, consequently, worthwhile only in the case of sufficientlyhigh production quantities of the shaped bodies to be producedtherewith. Since the mentioned Coriolis mass-flow/density sensor PromassF is manufactured in a number of different standard, nominal sizes up to100 mm, in each case in large production quantities, deep drawing of themetal caps is economical, even though a separate deep drawing die isrequired for each nominal size.

However, if, for certain nominal sizes, especially for nominal sizesgreater than 100 mm, but even for non-standard nominal sizes less than100 mm, only smaller production quantities are expected, then themanufacture of the metal caps by means of such deep drawing diesspecially sized for the individual nominal sizes cannot be practicallyrealized, because of the high costs.

SUMMARY OF THE INVENTION

An object of the invention is to provide a vibration-type sensor havinga metal cap which can be manufactured at lower cost than previouslypossible, particularly by cold forming. A further object of theinvention is to provide a method for connecting the metal cap with asupporting arrangement of a vibration-type measuring sensor permittingmanufacture of the sensor at lower total cost.

For solving these objects, the invention provides a vibration-typesensor for a fluid, the sensor being suitable for use in a pipeline atleast temporarily containing fluid flowing therethrough and including:

at least one curved measuring tube that vibrates during operation andguides the fluid, and

a metal housing enclosing the at least one measuring tube,

having a supporting arrangement of metal,

in which the at least one measuring tube is held at its inlet and outletends in a manner such that the tube can oscillate, and

out of which a measuring tube segment protrudes sideways, and

having a metal cap composed of a first cap half and a second cap halffor covering the measuring tube segment, or segments, as the case maybe,

an edge of which first cap half includes a first edge portion, a secondedge portion, a third edge portion, and a circular-arc-shaped fourthedge portion, and

an edge of which second cap half includes a fifth edge portion, a sixthedge portion, a seventh edge portion, and a circular-arc-shaped eighthedge portion,

wherein the first, second and third edge portions, respectively thefifth, sixth and seventh edge portions, are connected continuously withthe supporting arrangement, and

wherein the fourth and the eighth edge portions are connectedcontinuously with one another.

For solving the named objects, the invention provides further a methodfor producing a connection of a metal cap with a supporting arrangementof a vibration-type sensor for a fluid, the sensor being suitable foruse in a pipeline at least temporarily containing fluid flowingtherethrough and including:

at least one curved measuring tube that vibrates during operation andguides the fluid, and

a metal housing enclosing the at least one measuring tube,

having a supporting arrangement of metal,

in which the at least one measuring tube is held at its inlet and outletends in a manner such that the tube can oscillate, and

out of which a measuring tube segment protrudes sideways, and

having a metal cap composed of a first cap half and a second cap halffor covering the measuring tube segment, or segments, as the case maybe,

an edge of which first cap half includes a first edge portion, a secondedge portion, a third edge portion, and a fourth edge portion, and

an edge of which second cap half includes a fifth edge portion, a sixthedge portion, a seventh edge portion, and an eighth edge portion,

wherein the first, second and third edge portions, respectively thefifth, sixth and seventh edge portions, are to be connected continuouslywith the supporting arrangement, and

wherein the fourth and the eighth edge portions are to be connectedcontinuously with one another.

in which method

a segment is cut in such a manner out of a dish-shaped intermediatehaving a surrounding edge bead formed thereon,

that the first edge portion and the fourth edge portion, respectivelythe fifth edge portion and the eighth edge portion, and, at the edgebead, the second and the sixth, respectively the third and the seventhedge portions, are created,

a first of these segments is placed on the supporting arrangement forcovering a first half of the measuring tube part, or measuring tubeparts, as the case may be,

a second of these segments is placed on the supporting arrangement forcovering a second half of the measuring tube part, or measuring tubeparts, as the case may be, in such a manner,

that the fourth and the eighth edge portions lie opposite to oneanother,

the first, the second, the third, the fifth, the sixth and the seventhedge portions are welded completely to the supporting arrangement, and

the fourth edge portion is welded completely to the eighth edge portion.

According to a preferred development of the method, the intermediate isformed from a flat, circular sheet, which is provided with aquarter-torus-shaped edge bead by metal spinning.

An advantage of the invention is that, although by going back to the twocap halves (known per se) a connecting seam becomes necessary betweenthem, the costs of the deep drawing die for the metal cap are reduced tothe smaller manufacturing costs of the cap halves.

The invention will now be explained in greater detail on the basis ofthe figures of the drawing showing a preferred example of an embodiment.Functionally equivalent parts are given the same reference charactersthroughout the figures. However, reference characters are only repeatedin subsequent figures to the extent such is helpful.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a side view of a sensor in the form of a Coriolisflow/density/viscosity sensor.

FIG. 2 shows a front view of the sensor of FIG. 1.

FIG. 3 shows in perspective, and slightly from above, the sensor ofFIGS. 1 and 2, with a cap-half removed,

FIG. 4 shows in perspective, and slightly from below, the sensor of FIG.3.

FIG. 5 shows in perspective an intermediate used in making the caphalves, and

FIG. 6 shows finished cap halves in perspective.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1 to 4 show a vibration-type sensor 1, here a Coriolisflow/density/viscosity sensor, in various views, with FIG. 1 being aside view of the measuring sensor 1, FIG. 2 its front view, and FIGS. 3and 4 perspective views of the sensor 1 from two different viewingangles. FIGS. 1 to 4 are explained as a group in the following. Sensor 1is connected by way of flanges 2, 3 into the course of a pipeline of agiven diameter, containing a liquid gaseous or vaporous fluid to bemeasured flowing therethrough. For reasons of clarity, the pipeline isnot shown here. Instead of flanges, the sensor 1 can also be connectedinto the pipeline by other known means, such as e.g. Triclamp connectorsor screw connections.

The sensor has two parallel measuring tubes 4, 5 for guiding the fluid,which are each curved in a plane; it is also feasible to use only asingle measuring tube, or at least one measuring tube curved in a screwshape can be provided.

The measuring tubes 4, 5 are excited during operation intotuning-fork-like vibrations, preferably resonance vibrations, by anexciter arrangement usually at the crest of the measuring tubes 4, 5,this not being shown here for reasons of clarity. For the same reason,two sensor arrangements are also not shown, one of which is fixed on theinlet side on the measuring tubes 4, 5, and the other on the outletside, preferably at equal spacings from the crest.

The measuring tubes 4, 5 are enclosed by a housing, which is composed,on the one hand, of a supporting arrangement of metal, here a supportingtube 6, and, on the other hand, of a metal cap 7; the supporting tube 6is a cylinder of circular cross section in this embodiment.

The measuring tubes 4, 5 are held in the supporting arrangement, here inthe supporting tube 6, at their inlet and outlet ends in a manner suchthat the tubes can oscillate. Each measuring tube 4, 5 has a measuringtube segment protruding sideways out of the supporting arrangement. Ascan be seen in FIG. 3, the laterally protruding measuring tube segmentsextend through two cutouts 61, 62 of the supporting tube 6.

The metal cap 7 is composed of a first cap half 71 and a second cap half72; in FIGS. 3 and 4, the latter is not shown, in order that themeasuring tubes 4, 5 can be seen. The metal cap 7 composed of the twocap halves 71, 72 completely covers the measuring tube segments 4, 5 inthe finished state of the sensor 1, but does not contact them, in ordernot to disturb their vibrations. The parts of the sensor 1 inside of thehousing formed by the supporting arrangement, here by the supportingtube 6, and the metal cap 7 are hermetically sealed by the housing withrespect to the environment

The first cap half 71 has a peripheral edge 73 and the second cap half72 a peripheral edge 74; see FIG. 6. Edge 73 is composed of a first edgeportion 731, a second edge portion 732, a third edge portion 733 and acircular-arc-shaped fourth edge portion 734. Edge 74 is composed of afifth edge portion 741, a sixth edge portion 742, a seventh edge portion743 and a circular-arc-shaped eighth edge portion 744. The edge portions731, 741 are preferably straight in the illustrated embodiment, butother lines are possible.

The edge portions 732, 733, 742, 743 can be straight, when e.g. thesupporting arrangement has a square or rectangular cross section, sothat these edge portions abut on the associated flat lateral surfacesand are connected therewith. Even in the case of the cylindricalsupporting tube 6 of the embodiment, its lateral surface can be providedwith a flat abutment surface, so that the edge portions 732, 733, 742,743 can be straight.

The edge portions 731, 732, 733 of the edge 73 and the edge portions741, 742, 743 of the edge 74 are continuously connectable, here welded,with the supporting arrangement, here the supporting tube 6. The edgeportions 734, 744 are continuously connected, here, likewise, welded, toone another.

The edge portions 731, 741 are, as mentioned, straight in thisembodiment, have a length L and lie on the lateral surface of supportingtube 6, along elements of the lateral surface. The edge portions 734,744 have the shape of a circular arc of radius R, whose height H isgreater than the maximum separation of the measuring tube segments fromthe center line of the supporting tube 6. The exact form of the edgeportions 732, 733, 742, 743 is explained further in connection with theexplanation of the manufacture of the cap halves 71, 72.

Finally, in FIG. 1, there is an electronics housing 9 mounted on thesupporting arrangement, here on the supporting tube 6, by means of aneck-like connecting place 8. Housing 9 contains the measuring andoperational circuit for the sensor 1. This circuit produces, on the onehand, an exciter signal driving the mentioned exciter arrangement and,on the other hand, receives the signals of the mentioned sensorarrangements and generates therefrom desired signals representing massflow, density, viscosity or temperature of the flowing fluid, whichsignals can be processed further or displayed.

FIGS. 3 and 4 omit the connecting piece 8 and the electronics housing 9;FIG. 4 does show the seating surface 63 for the connecting piece 8. Anelectrical conduit 64 is arranged in the seating surface 63 and enableselectrical connections for the abovementioned exciter arrangement andfor the above-mentioned sensor arrangements, as well as for otherelectrical components which may be present, such as e.g. temperaturesensors.

An example of an embodiment of a method for creating a connectionbetween the metal cap 7 and the supporting arrangement, hem thesupporting tube 6, of the vibration-type sensor 1 will now be explainedon the basis of FIGS. 5 and 6. This connection method is based on adish-shaped intermediate having a surrounding, continuous, peripheraledge bead.

In the embodiment, the intermediate is an essentially circularintermediate 70 formed from a flat, circular sheet, which, by metalspinning, is provided with a quarter-torus-shaped edge bead 701.

Metal spinning involves a cold forming of metals, wherein a sheet to beformed is pressed by means of appropriately formed rollers into a formof wood or metal. Either the sheet rotates and the rollers are fixed inspace, although they each can rotate on a journal axis; or the sheet isfixed and the rollers rotate about a principal axis, in addition totheir rotation about their journal axes.

While FIG. 5 shows a circular intermediate 70, it can have any othersuitable shape, e.g. that of a square or a rectangle. To form the edgebead in these other cases, the edges of the sheet can be, so-to-say,flipped up, to included angles between about 150° and preferably 90°, sothat a square or rectangular box is formed.

Such a box can have the advantage compared with the circularintermediate 70, that, with appropriate dimensioning, cap halves can becut from it for more than a single nominal size. Due, however, to theoptical impression of the vibration sensor 1 achieved with the circularintermediate 70, thus on the basis of its attractive design, thecircular intermediate 70 is preferably used.

After the intermediate, here the circular intermediate 70, has beenmanufactured, as many segments are cut from it, as is shown in FIG. 6,as its dimensions permit; in FIG. 6, three such segments are illustratedas possible, of which two are used for a first sensor and the thirdsegment for a second sensor.

Preferably, the cutting is done by laser cutting in an appropriatecutting device; this makes it possible to obtain every desired shape ofedge on a segment to be cut out. The cutting of the segments from theintermediate produces the edge portions 731, 732, 733, 734, respectively741, 742, 743, 744, already described above. This cutting feature isespecially important, when, as in the illustrated embodiment, on the onehand, the edge bead 701 is of quarter-torus-shape, and, on the otherhand, the supporting arrangement is in the form of a cylindricalsupporting tube 6. In such case, the spatial shapes of the edge portions732, 733, 742, 743 following the lateral surface of the supporting tube6 are given by the spatial intersection curves of the always circularcross sections of the supporting tube 6 with the quarter-torus-shapededge bead 701. Such is indicated by way of example by arrow 733′ in FIG.3.

From the already mentioned condition that the cap halves 71, 72 must notinterfere with the vibrations of the measuring tubes 4, 5, i.e. thusthat the tubes must oscillate freely, and, consequently, that there mustbe a safety spacing s for the metal cap, the dimensioning of theintermediate, especially the circular intermediate 70 with thequarter-torus-shaped edge bead 701, can be specified as follows.

The parameters, as already defined above, of length L of the edgeportions 731, 741, height H of the circular arc of the edge portions734, 744, as well as the radius r of the quarter torus, see FIG. 2, mustbe chosen such that the following conditions are maintained:

L greater than the distance A of the inlet-side border of the cutout 61from the outlet-side border of the cutout 62, see FIG. 3, or greaterthan a corresponding distance in the case of a differently shapedsupporting arrangement,

H greater than the distance of the crest of the measuring tube segmentsfrom the centerline 65 of the support arrangement, plus safety spacings,

r equal to twice the outer diameter of a measuring tube, plus the mutualseparation of the measuring tubes—in the case where more than onemeasuring tube is present—plus 2s.

The cutting out of the segments 71, 72 is performed such that the edge731 respectively the edge 734 and at the edge bead 701 the edge portion732 and the edge portion 741 respectively the edge portion 733 and theedge portion 743 are created. A first of these segments is placed on thesupporting arrangement, here the supporting tube 6, for covering a firsthalf of the measuring tube part, or measuring tube parts, as the casemay be. A second of these segments is likewise placed on the supportingarrangement, here again the supporting tube 6, for covering a secondhalf of the measuring tube part, or measuring tube parts, as the casemay be, in such a manner that the fourth edge portion 734 and the eighthedge portion 744 lie opposite to one another. The edge portions 731,732, 733, 741, 742, 743 are then completely welded to the supportingarrangement, here to the supporting tube 6, and likewise the edgeportion 734 to the edge portion 744.

1. A vibration-type sensor for a fluid, the sensor being suitable foruse in a pipeline at least temporarily containing fluid flowingtherethrough, comprising: at least one curved measuring tube thatvibrates during operation and guides the fluid; and a metal housingenclosing said at least one measuring tube, said metal housing having asupporting arrangement of metal, in which said at least one curvedmeasuring tube is held at its inlet and outlet ends in a manner suchthat the tube can oscillate, and out of which a segment of said at leastone curved measuring tube protrudes sideways, and having a metal capcomposed of a first cap half and a second cap half for covering said atleast one curved measuring tube segment, or segments, an edge of saidfirst cap half including a first edge portion, a second edge portion, athird edge portion, and a circular-arc-shaped fourth edge portion, andan edge of said second cap half including a fifth edge portion, a sixthedge portion, a seventh edge portion, and a circular-arc-shaped eighthedge portion, wherein said first, second and third edge portions,respectively, said fifth, sixth and seventh edge portions, are connectedcontinuously with said supporting arrangement, and said fourth andeighth edge portions are connected continuously with one another.